Workflows developed to process pollen data to estimate components of ecosystem change
Alistair Seddon
Ondřej Mottl
PAGES Planetary Boundaries Working Group
- Holocene variability is a key component of planetary boundaries concept
- Focus on temporal dynamics/ safe operating spaces
- “To meet the challenge of maintaining the Holocene state, we propose a framework based on ‘planetary boundaries’. These boundaries define the safe operating space for humanity with respect to the Earth system and are associated with the planet’s biophysical subsystems or processes.” Steffen et al. 2009
Introduction
- How can we use palaeoecological (and related fields) data to address the planetary boundaries concept?
Example from pollen data
- Focus on temporal dynamics
- We need a metric (or series of metrics that can reflect something related to the planetary boundary)
- We need a method for describing the variability (e.g. using a generalised additive model)
- If we are talking global planetary boundaries, we need to look at multiple records, so need a reproducible method to show how to do this.
Diversity metrics
- Richness, evenness etc., can be estimated using Hill Numbers
- One component of ‘Ecosystem Condition’ (see, e.g. Dearing et al. 2014)
- Other metrics are available!
GAMs
- Statistical model to show non-linear trends through time
- Gavin Simpson has done the groundwork to transfer this method to palaeoecological data (Simpson 2018, Presentation on Wednesday, 11-11.15)
- Models a trend (e.g. diversity against time) using a series of basis functions, allowing non-linear trends to be fit to data
GAMs
- ‘Generalised’ framework means it is highly flexible, used on multiple data types
- Note that it doesn’t necessarily tell us where we should draw the boundary, but it does give us a statistically robust description of the variability which we can then use to make informed decisions
GAMs
Reproducible workflows
- If integrating across multiple sites then it is important to have standardized data that are comparable
- In pollen this means- same depositional environment, same age-depth models, same levels of taxonomic harmonisation, (same/ similar temporal resolution), comparable temporal ranges etc.
- We have been developing reproducible workflows for pollen data in the HOPE project, we will show an example of this today (see Ondrej’s poster)